As used in the well drilling and servicing industry, a blowout preventer is a device such as may be attached to the casing of a well to seal off the annular space between the casing and tubing disposed within the casing so as to contain and control the flow of liquids or gases under high pressure that may be encountered when drilling or servicing the well. A conventional blowout preventer comprises a housing with hydraulic rams connected to opposite sides thereof for movement toward and away from each other inside of the housing. Carried on the ends of the rams within the housing are sealing blocks suitably sized and shaped to engage and seal against the tubing extending through the housing as well as against an interior wall of the housing. The sealing blocks are connected removably with the rams and may be changed through two openings in one or more sides of the housing to accommodate different sizes of tubing or for reasons of wear. In service use, one or more doors are connected to the housing to close the openings and, in prior blowout preventers, these doors are bolted to the housing.